<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      body > div {
        width: 600px;
        height: 50px;
      }
      .header {
        background-color: black;
      }
      .contont {
        height: 200px;
      }
      .contont > div {
        float: left;
        width: 200px;
        height: 200px;
      }
      .lc {
        background-color: red;
      }
      .cc {
        background-color: yellow;
      }
      .rc {
        background-color: blue;
      }
      .footer {
        background-color: green;
      }
    </style>
  </head>
  <body>
    <div class="header"></div>
    <div class="contont">
      <div class="lc"></div>
      <div class="cc"></div>
      <div class="rc"></div>
    </div>
    <div class="footer"></div>
  </body>
</html>
